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Previously, commit8388f7df93("iommu/amd: Do not support IOMMU_DOMAIN_IDENTITY after SNP is enabled") prevented users from changing the IOMMU domain to identity if SNP was enabled. This resulted in an error when writing to sysfs: # echo "identity" > /sys/kernel/iommu_groups/50/type -bash: echo: write error: Cannot allocate memory However, commit4402f2627d("iommu/amd: Implement global identity domain") changed the flow of the code, skipping the SNP guard and allowing users to change the IOMMU domain to identity after a machine has booted. Once the user does that, they will probably try to bind and the device/driver will start to do DMA which will trigger errors: iommu ivhd3: AMD-Vi: Event logged [ILLEGAL_DEV_TABLE_ENTRY device=0000:43:00.0 pasid=0x00000 address=0x3737b01000 flags=0x0020] iommu ivhd3: AMD-Vi: Control Reg : 0xc22000142148d AMD-Vi: DTE[0]: 6000000000000003 AMD-Vi: DTE[1]: 0000000000000001 AMD-Vi: DTE[2]: 2000003088b3e013 AMD-Vi: DTE[3]: 0000000000000000 bnxt_en 0000:43:00.0 (unnamed net_device) (uninitialized): Error (timeout: 500015) msg {0x0 0x0} len:0 iommu ivhd3: AMD-Vi: Event logged [ILLEGAL_DEV_TABLE_ENTRY device=0000:43:00.0 pasid=0x00000 address=0x3737b01000 flags=0x0020] iommu ivhd3: AMD-Vi: Control Reg : 0xc22000142148d AMD-Vi: DTE[0]: 6000000000000003 AMD-Vi: DTE[1]: 0000000000000001 AMD-Vi: DTE[2]: 2000003088b3e013 AMD-Vi: DTE[3]: 0000000000000000 bnxt_en 0000:43:00.0: probe with driver bnxt_en failed with error -16 To prevent this from happening, create an attach wrapper for identity_domain_ops which returns EINVAL if amd_iommu_snp_en is true. With this commit applied: # echo "identity" > /sys/kernel/iommu_groups/62/type -bash: echo: write error: Invalid argument Fixes:4402f2627d("iommu/amd: Implement global identity domain") Signed-off-by: Joe Damato <joe@dama.to> Reviewed-by: Vasant Hegde <vasant.hegde@amd.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>